15. Parameter expansion

• https://www.gnu.org/software/bash/manual/html_node/Shell-Parameter-Expansion.html

15.1. Simple usage

• $PARAMETER

• ${PARAMETER}

15.2. Indirection

• ${!PARAMETER}

15.3. Case modification

• ${PARAMETER^}

• ${PARAMETER^^}

• ${PARAMETER,}

• ${PARAMETER,,}

• ${PARAMETER~}

• ${PARAMETER~~}

15.4. Variable name expansion

• ${!PREFIX*}

• ${!PREFIX@}

15.5. Substring removal (also for filename manipulation!)

• ${PARAMETER#PATTERN}

• ${PARAMETER##PATTERN}

• ${PARAMETER%PATTERN}

• ${PARAMETER%%PATTERN}

15.6. Search and replace

• ${PARAMETER/PATTERN/STRING}

• ${PARAMETER//PATTERN/STRING}

• ${PARAMETER/PATTERN}

• ${PARAMETER//PATTERN}

15.7. String length

• ${#PARAMETER}

15.8. Substring expansion

• ${PARAMETER:OFFSET}

• ${PARAMETER:OFFSET:LENGTH}

15.9. Use a default value

• ${PARAMETER:-WORD}

• ${PARAMETER-WORD}

15.10. Assign a default value

• ${PARAMETER:=WORD}

• ${PARAMETER=WORD}

15.11. Use an alternate value

• ${PARAMETER:+WORD}

• ${PARAMETER+WORD}

15.12. Display error if null or unset

• ${PARAMETER:?WORD}

• ${PARAMETER?WORD}